Cooling System for Molded Modules and Corresponding Manufacturing Methods

ABSTRACT

A cooling system for molded modules includes a plurality of individual modules each including a semiconductor die encapsulated by a mold compound, a plurality of leads electrically connected to the semiconductor die and at least partly uncovered by the mold compound, and a cooling plate at least partly uncovered by the mold compound. A molded body surrounds a periphery of each individual module to form a multi-die module. The leads of each individual module and the cooling plates are at least partly uncovered by the molded body. A lid with a port is attached to a periphery of the molded body at a first side of the multi-die module. The lid seals the multi-die module at the first side to form a cavity between the lid and the molded body for permitting fluid exiting or entering the port to contact the cooling plates of each individual module.

TECHNICAL FIELD

The instant application relates to power modules, and more particularlyto cooling systems for power modules.

BACKGROUND

Power modules with double-side cooling significantly improve the thermalperformance of the package by reducing thermal resistance, and therebyincreasing the power density of the entire system. However, powermodules with double-sided cooling present a challenge with regard tointegrating a heat-sink with the module. The design of the cooler oftenis a critical issue in achieving the highest possible performance. Forexample, the cooling fluid should be distributed in two differentchannels above and below the power modules included in the package toincrease the thermal performance of the package. Also, the entire systemmust be watertight. The heat sink should be robust, low-cost andlightweight.

Conventional double-sided module cooling technologies require additionalparts such as O-rings and bolts or screws to achieve a water-tightsystem. Conventional aluminum coolers also use thicker aluminum blocks.Still further components are typically needed to achieve a watertightheat-sink and bi-directional coolant distribution. These additionalparts increase the system weight and cost and still present a real riskof fluid leakage. Furthermore, the need for many assembly stepsincreases production cost.

SUMMARY

Embodiments described herein provide a plastic molded cooling systemwithout bolt connections and O-rings. The cooling system has a muchlower risk of fluid leakage and higher design flexibility compared toconventional power module cooling systems, significantly reducing systemcost, the number of assembly steps and system weight.

According to an embodiment of a cooling system for molded modules, thecooling system comprises a plurality of individual modules eachcomprising a semiconductor die encapsulated by a mold compound, aplurality of leads electrically connected to the semiconductor die andat least partly uncovered by the mold compound, and a cooling plate atleast partly uncovered by the mold compound. The cooling system furthercomprises a molded body surrounding a periphery of each individualmodule to form a multi-die module. The leads of each individual moduleand the cooling plates are at least partly uncovered by the molded body.A lid with a port is attached to a periphery of the molded body at afirst side of the multi-die module. The lid seals the multi-die moduleat the first side to form a cavity between the lid and the molded bodyfor permitting fluid exiting or entering the port to contact the coolingplates of each individual module.

According to an embodiment of a method of manufacturing a cooling systemfor molded modules, the method comprises: providing a plurality ofindividual modules each comprising a semiconductor die encapsulated by amold compound, a plurality of leads electrically connected to thesemiconductor die and at least partly uncovered by the mold compound,and a cooling plate at least partly uncovered by the mold compound;forming a molded body surrounding a periphery of each individual moduleto form a multi-die module with the leads of each individual module andthe cooling plates being at least partly uncovered by the molded body;and attaching a lid with a port to a periphery of the molded body at afirst side of the multi-die module, the lid sealing the multi-die moduleat the first side to form a cavity between the lid and the molded bodyfor permitting fluid exiting or entering the port to contact the coolingplates of each individual module.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts. In the drawings:

FIGS. 1 through 3, including FIGS. 2A through 2C and 3A and 3B,illustrate different steps of an embodiment of a method of manufacturinga cooling system for molded modules;

FIGS. 4A through 4E illustrate different views of a cooling system formolded modules according to an embodiment; and

FIGS. 5A and 5B illustrate different views of a cooling system formolded modules according to another embodiment.

DETAILED DESCRIPTION

According to embodiments described herein, a cooling system for moldedmodules is provided. The cooling system comprises a plurality ofindividual modules. Each module comprises a semiconductor dieencapsulated by a mold compound, a plurality of leads electricallyconnected to the semiconductor die and at least partly uncovered by themold compound, and a cooling plate at least partly uncovered by the moldcompound. The cooling system further comprises a molded body surroundinga periphery of each individual module to form a multi-die module. Theleads of each individual module and the cooling plates are at leastpartly uncovered by the molded body. A lid with a port is attached tothe periphery of the molded body at a first side of the multi-diemodule. The lid seals the multi-die module at the first side to form acavity between the lid and the molded body for permitting fluid exitingor entering the port to contact the cooling plates of each individualmodule. The cooling system does not require bolt connections or O-rings.As such, the cooling system has a much lower risk of fluid leakage andhigher design flexibility compared to conventional power module coolingsystems, significantly reducing system cost, the number of assemblysteps and system weight.

FIGS. 1 through 3 illustrate an embodiment of method of manufacturingthe cooling system. According to this embodiment, a plurality ofindividual modules 100 is provided as shown in FIG. 1. The modules 100can be purchased or manufactured. In either case, each module 100comprises a semiconductor die encapsulated by a mold compound 102 suchas an epoxy, a plurality of leads 104 electrically connected to thesemiconductor die and at least partly uncovered by the mold compound102, and a cooling plate 106 at least partly uncovered by the moldcompound 102. The leads 104 provide the necessary electrical connectionsto the semiconductor die. The leads 104 can be of the lead-frame typewhich protrude out from the mold compound 102 of the modules 100 asshown in FIG. 1. Other types of leads 104 can be used such as the kindused in surface-mount modules, e.g. gull-wing, J-lead or flat leads.

The semiconductor die included in the individual modules 100 andconnected to the leads 104 can be any type of semiconductor dierequiring liquid cooling during operation such as an IGBT (insulatedgate bipolar transistor) die, power MOSFET (metal oxide semiconductorfield effect transistor) die, JFET (junction field effect transistor)die, GaN die, SiC die, thyristor die, power diode die, etc. More thanone semiconductor die can be included in some or all of the modules 100,as well as passive components. The semiconductor dies can form any typeof desired circuit such as a half-bridge, full-bridge or 3-phasecircuit, etc.

Each individual module 100 can have a single cooling plate 106 at oneside of the module 100, or a pair of spaced apart cooling plates 106 atopposing sides of the module 100 with the corresponding semiconductordie interposed between the pair of cooling plates 106 (the bottom modulecooling plates are out of view in FIG. 1). In either case, the modulecooling plates 106 remain at least partly uncovered by the mold compound102 of the corresponding module 100.

Continuing with the manufacturing process, a molded body 108 is formed,e.g. by injection molding which surrounds the periphery of eachindividual module 100 to form a multi-die module 110. FIG. 2A shows thetop side 109 of the multi-die module 110 and FIG. 2B shows the bottomside 111. FIG. 2C shows an enlarged partial cross-sectional view of themulti-die module 110 along the line labeled A-A in FIG. 2A. Theindividual modules 100 included in the multi-die module 110 each have apair of spaced apart cooling plates 106 according to this embodiment, aspreviously described herein. The cooling plates 106 at the top side 109of the multi-die module 110 and the cooling plates 106 at the bottomside 111 of the multi-die module 110 remain at least partly uncovered bythe molded body 108. The leads 104 of each individual module 100 alsoremain at least partly uncovered by the molded body 108. In the case oflead-frame type or similar leads, the leads 104 of each individualmodule 100 protrude out of the molded body 108 as shown in FIGS. 2A and2B. A different module lead configuration is possible with other typesof module leads 104 such as surface-mount leads. In each case,electrical connections can be made to the individual modules 100 and theindividual modules 100 can be directly cooled at the exposed side 107 ofthe cooling plates 106.

In one embodiment, the molded body 108 has open recessed regions 112over the cooling plates 106 so that the cooling plates 106 remain atleast partly uncovered by the molded body 108. The molded body 108 canhave open passageways 114 at opposing ends of the molded body 108. Sucha multi-die module construction permits a fluid to flow in directcontact with the cooling plates 106 at both sides 109, 111 of themulti-die module 110 as described in more detail later herein.

A lid 116 with at least one port 118, 120 is then attached to theperiphery of the molded body 108 at a first (e.g. top) side 109 of themulti-die module 110. FIG. 3A shows the cooling system during the lidattach process, and FIG. 3B shows the cooling system after the lid 116is attached to the periphery of the molded body 108. The lid 116 sealsthe multi-die module 110 at the first side 109 to form a cavity (out ofview in FIGS. 3A and 3B) between the lid 116 and the molded body 108.The cavity permits fluid exiting or entering one of the ports 118, 120in the lid 116 to contact the cooling plates 106 of each individualmodule 100 included in the multi-die module 110. A base plate 122 isattached to the periphery of the molded plastic body 108 at the second(e.g. bottom) side 111 of the multi-die module 110. The base plate 122seals the multi-die module 110 at the second side 111 of the multi-diemodule 110.

In one embodiment, the lid 116 and the base plate 122 each compriseplastic. According to this embodiment, the lid 116 and base plate 122are attached to the periphery of the molded body 108 at opposing mainsides 109, 111 of the multi-die module 110 by positioning the base plate122 on a support base 124 such as a jig so that openings 126 in the baseplate 122 align with corresponding posts 128 of the support base 124.The molded body 108 is positioned on the base plate 122 so that openings130 in the molded body 108 align with the posts 128 of the support base124, and the lid 116 is positioned on the molded body 108 so thatopenings 132 in the lid 116 align with the posts 128 of the support base124. The lid 116 is then plastic welded to the periphery of the moldedbody 108 at the first side 109 of the multi-die module 110, and the baseplate 122 is plastic welded to the periphery of the molded body 108 atthe second (opposing) side 111 of the multi-die module 110.

In another embodiment, the lid 116 and base plate 122 are attached tothe periphery of the molded body 108 at opposing sides 109, 111 of themulti-die module 110 by over-molding. Over-molding is an injectionmolding process where two materials are molded together. The lid 116 andbase plate 122 can be plastic or another material such as metal (e.g.aluminum) according to this embodiment. In each case, the over-moldedlid 116 and base plate 122 seal the multi-die module 100 at the opposingmain sides 109, 111 of the multi-die module 110 and form the coolantcavity between the molded body 108 and the lid 116 and base plate 122.In yet another embodiment, the lid 116 and base plate 122 are attachedto the periphery of the molded body 108 at the opposing sides 109, 111of the multi-die module 110 by gluing, e.g. using an adhesive.

FIGS. 4A through 4E show different views of the cooling system aftermanufacturing. FIG. 4A shows the top side of the cooling system. FIG. 4Bshows the bottom side of the cooling system. FIG. 4C shows across-sectional view of the cooling system along the line labeled B-B inFIG. 4A. FIG. 4D shows an enlarged partial cross-sectional view of thecooling system along the line labeled C-C in FIG. 4C. FIG. 4E shows across-sectional view of the cooling system along the line labeled B-B inFIG. 4A with fluid flowing in the cavity of the cooling system.

The cooling system includes the individual modules 100, the molded body108 surrounding the periphery of each individual module 100 to form amulti-die module 110 (with the leads 104 of each individual module 100and the cooling plates 106 being at least partly uncovered by the moldedbody 108), and the lid 116 attached to the periphery of the molded body108 at a first (e.g. top) side 109 of the multi-die module 110 and thebase plate 122 attached to the periphery of the molded plastic body 108at the opposing (e.g. bottom) side 111 of the multi-die module 110. Thelid 116 seals the multi-die module 110 at the first side 109 and thebase plate 122 seals the multi-die module 110 at the opposing side 111.Upon attachment to the molded body 108, the lid 116 and the base plate122 form a cavity 200 between the molded body 108 and the lid 116 andbase plate 122. The cavity 200 permits fluid exiting or entering one ofthe ports 118, 120 in the lid 116 to contact the cooling plates 106 ofeach individual module 100.

The cavity 200 has a first part 202 between the lid 116 and the moldedbody 108 and a second part 204 between the base plate 122 and the moldedbody 108 according to the double-sided cooling embodiment illustrated inFIGS. 4A through 4E. According to this embodiment, the molded body 108has an open passageway 114 at opposing ends of the molded body 108 whichconnect the first and second parts 202, 204 of the cavity 200. This way,fluid can circulate in contact with the cooling plates 106 at both thetop and bottom sides 109, 111 of the multi-die module 110. The lid 116has an inlet port 118 for in-taking fluid into the first and secondparts 202, 204 of the cavity 200 in parallel and an outlet port 120 atthe same side as the inlet port 120 for exhausting the fluid from thefirst and second parts 202, 204 of the cavity 200 in parallel. Theparallel fluid flow path is illustrated in FIG. 4E with arrows. Thecooling plates 106 can have surface structures such as pins, fins or anintentionally roughened surface at a side 107 of the cooling plates 106open to the cavity 200 for increasing the turbulence of the fluidflowing in the cavity over the cooling plates 106.

FIGS. 5A and 5B show different views of the cooling system according toanother embodiment. FIG. 5A shows a perspective view of the coolingsystem, and FIG. 5B shows a cross-sectional view of the cooling systemalong the line labeled D-D in FIG. 5A. According to this embodiment, thecooling system includes a first lid 300 attached to the periphery of themolded plastic body 108 at a first (e.g. top) side 109 of the multi-diemodule 110 and a second lid 302 attached to the periphery of the moldedplastic body 108 at the opposing (e.g. bottom) side 111 of the multi-diemodule 110. The lids 300, 302 collectively seal the multi-die module 110at the opposing main sides 109, 111 of the multi-die module 110. Bothlids 300, 302 have a port 304, 306. For example, the port 304 in thefirst lid 300 can be the inlet port and the port 306 in the second lid302 can be the outlet port or vice-versa. The inlet port 304 intakes afluid into the first and second parts 202, 204 of the cavity 200 inseries. The outlet port 306 likewise exhausts the fluid from the firstand second parts 202, 204 of the cavity 200 in series. The series fluidflow path is illustrated in FIG. 5B with arrows. According to thisembodiment, the molded body 108 has an open passageway 114 at only oneend of the molded body 108 to ensure a series fluid flow.

Spatially relative terms such as “under”, “below”, “lower”, “over”,“upper” and the like, are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the device in additionto different orientations than those depicted in the figures. Further,terms such as “first”, “second”, and the like, are also used to describevarious elements, regions, sections, etc. and are also not intended tobe limiting. Like terms refer to like elements throughout thedescription.

As used herein, the terms “having”, “containing”, “including”,“comprising” and the like are open-ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

With the above range of variations and applications in mind, it shouldbe understood that the present invention is not limited by the foregoingdescription, nor is it limited by the accompanying drawings. Instead,the present invention is limited only by the following claims and theirlegal equivalents.

What is claimed is:
 1. A cooling system for molded modules, comprising:a plurality of individual modules each comprising a semiconductor dieencapsulated by a mold compound, a plurality of leads electricallyconnected to the semiconductor die and at least partly uncovered by themold compound, and a cooling plate at least partly uncovered by the moldcompound; a molded body surrounding a periphery of each individualmodule to form a multi-die module, with the leads of each individualmodule and the cooling plates being at least partly uncovered by themolded body; and a lid with a port attached to a periphery of the moldedbody at a first side of the multi-die module, the lid sealing themulti-die module at the first side to form a cavity between the lid andthe molded body for permitting fluid exiting or entering the port tocontact the cooling plates of each individual module.
 2. The coolingsystem of claim 1, wherein each individual module has a pair of spacedapart cooling plates at opposing sides of the individual module with thesemiconductor die interposed between the pair of cooling plates, whereineach pair of cooling plates is at least partly uncovered by the moldedbody at opposing first and second sides of the multi-die module, andwherein each pair of cooling plates is open to the cavity.
 3. Thecooling system of claim 2, further comprising a base plate attached tothe periphery of the molded plastic body at the second side of themulti-die module, the base plate sealing the multi-die module at thesecond side of the multi-die module.
 4. The cooling system of claim 3,wherein the cavity comprises a first part between the lid and the moldedbody and a second part between the base plate and the molded body, andwherein the molded body has an open passageway at opposing ends of themolded body which connect the first and second parts of the cavity. 5.The cooling system of claim 4, wherein the port of the lid is an inletport configured to intake a fluid into the first and second parts of thecavity in parallel, and wherein the lid further has an outlet port atthe same side as the inlet port configured to exhaust the fluid from thefirst and second parts of the cavity in parallel.
 6. The cooling systemof claim 4, further comprising an additional lid attached to theperiphery of the molded plastic body at the second side of the multi-diemodule, the additional lid sealing the multi-die module at the secondside of the multi-die module, wherein the port of the lid is configuredto intake a fluid into the first and second parts of the cavity inseries, and wherein the additional lid has an outlet port configured toexhaust the fluid from the first and second parts of the cavity inseries.
 7. The cooling system of claim 1, wherein the leads of eachindividual module protrude out of the molded body.
 8. The cooling systemof claim 1, wherein the lid comprises plastic and is plastic welded tothe periphery of the molded body to seal the multi-die module at thefirst side of the multi-die module and form the cavity between the lidand the molded body.
 9. The cooling system of claim 1, wherein the lidis over-molded to the periphery of the molded body to seal the multi-diemodule at the first side of the multi-die module and form the cavitybetween the lid and the molded body.
 10. The cooling system of claim 1,wherein the lid is attached to the periphery of the molded body by anadhesive to seal the multi-die module at the first side of the multi-diemodule and form the cavity between the lid and the molded body.
 11. Thecooling system of claim 1, wherein the cooling plates have surfacestructures at a side of the cooling plates open to the cavity forincreasing the turbulence of fluid flowing in the cavity over thecooling plates.
 12. A method of manufacturing a cooling system formolded modules, the method comprising: providing a plurality ofindividual modules each comprising a semiconductor die encapsulated by amold compound, a plurality of leads electrically connected to thesemiconductor die and at least partly uncovered by the mold compound,and a cooling plate at least partly uncovered by the mold compound;forming a molded body surrounding a periphery of each individual moduleto form a multi-die module with the leads of each individual module andthe cooling plates being at least partly uncovered by the molded body;and attaching a lid with a port to a periphery of the molded body at afirst side of the multi-die module, the lid sealing the multi-die moduleat the first side to form a cavity between the lid and the molded bodyfor permitting fluid exiting or entering the port to contact the coolingplates of each individual module.
 13. The method of claim 12, whereineach individual module has a pair of spaced apart cooling plates atopposing sides of the individual module with the semiconductor dieinterposed between the pair of cooling plates, wherein each pair ofcooling plates is at least partly uncovered by the molded body atopposing first and second sides of the multi-die module, and whereineach pair of cooling plates is open to the cavity.
 14. The method ofclaim 13, further comprising attaching a base plate to the periphery ofthe molded plastic body at the second side of the multi-die module, thebase plate sealing the multi-die module at the second side of themulti-die module.
 15. The method of claim 14, wherein the cavitycomprises a first part between the lid and the molded body and a secondpart between the base plate and the molded body, and wherein the moldedbody has an open passageway at opposing ends of the molded body whichconnect the first and second parts of the cavity.
 16. The method ofclaim 15, wherein the port of the lid is an inlet port configured tointake a fluid into the first and second parts of the cavity inparallel, and wherein the lid further has an outlet port at the sameside as the inlet port configured to exhaust the fluid from the firstand second parts of the cavity in parallel.
 17. The method of claim 15,further comprising attaching an additional lid to the periphery of themolded plastic body at the second side of the multi-die module, theadditional lid sealing the multi-die module at the second side of themulti-die module, wherein the port of the lid is configured to intake afluid into the first and second parts of the cavity in series, andwherein the additional lid has an outlet port configured to exhaust thefluid from the first and second parts of the cavity in series.
 18. Themethod of claim 14, wherein the lid and the base plate each compriseplastic, and wherein attaching the lid to the periphery of the moldedbody at the first side of the multi-die module and attaching the baseplate to the periphery of the molded plastic body at the second side ofthe multi-die module comprises: positioning the base plate on a supportbase so that openings in the base plate align with corresponding postsof the support base; positioning the molded body on the base plate sothat openings in the molded body align with the posts of the supportbase; positioning the lid on the molded body so that openings in the lidalign with the posts of the support base; plastic welding the lid to theperiphery of the molded body at the first side of the multi-die module;and plastic welding the base plate to the periphery of the molded bodyat the second side of the multi-die module.
 19. The method of claim 12,wherein the lid is a plastic lid and attaching the lid to the peripheryof the molded body comprises plastic welding the plastic lid to theperiphery of the molded body to seal the multi-die module at the firstside of the multi-die module and form the cavity between the lid and themolded body.
 20. The method of claim 12, wherein attaching the lid tothe periphery of the molded body comprises over-molding the lid to theperiphery of the molded body to seal the multi-die module at the firstside of the multi-die module and form the cavity between the lid and themolded body.
 21. The method of claim 12, wherein attaching the lid tothe periphery of the molded body comprises gluing the lid to theperiphery of the molded body to seal the multi-die module at the firstside of the multi-die module and form the cavity between the lid and themolded body.